Method for accurately measuring real-time dew-point value and total moisture content of a material

ABSTRACT

A system and method for accurately measuring the real-time valid dew-point value of a material and determining the total moisture content of the material within the valid dew-point value by using an algorithm during the material drying process. The algorithm estimates the valid dew-point value of the material and the total moisture content of the material by analyzing the sensor data received on a server. The algorithm determines a valid dew-point value by estimating an inflection point for the material, and the total moisture content of the material is determined within the valid dew-point value.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to the U.S. Provisional Patentapplication No. 62/119,293 filed in the United States Patent andTrademark Office on Feb. 23, 2015, entitled “Method for AccuratelyMeasuring Real-Time Dew-Point Value and Total Moisture Content of aMaterial”. The specification of the above referenced patent applicationis incorporated herein by reference in its entirety.

FIELD OF INVENTION

The present invention relates generally to a method of accuratelymeasuring real-time dew-point value and total moisture content of amaterial. More specifically, it relates to accurately measuring thereal-time valid dew-point value and estimating the total moisturecontent of the material within the valid dew-point value using analgorithm during a material drying process.

BACKGROUND

Currently, the existing material drying processes adopt variousmechanisms to determine the real-time dew-point value of a material andto estimate the total moisture content of the material. However, theseprocesses do not provide an accurate real-time dew-point estimate as thedew-point of the material may vary over a period during the materialdrying process. Further, the existing drying process does not allow thesystem to provide a valid dew-point value within which the system mustbe capable of estimating the total moisture content of the material.

PCT publication no. WO2013093942 discloses a method and a device formoisture determination and control using real-time measurement of thematerial moisture content at an inlet and outlet of the drying process,such as in a drying hopper. Here, the drying process is controlled byanticipating the drying load based on the moisture content of theincoming material to be dried.

CN 103399486 discloses a temperature optical energy-saving controlmethod for a plastic dryer. The method adopts a predictive controlstrategy based on multi-model switching to identify dynamiccharacteristics of air temperature of the plastic dryer and establish aswitching system model of an object under each typical workingcondition. An optical target function with constraint is established byutilizing a switching rule and a mixed neural network is formed byneural networks for processing a continuous variable and a discretebinary variable together.

U.S. Pat. No. 8,433,443 B2 relates to a method for online monitoring ofpolymerization reaction in a fluid bed reactor to generate dataindicative of imminent occurrence of a discontinuity event (such assheeting). The method further relates to optional control of thereaction to prevent the occurrence of the discontinuity event.

CN 201672991 relates to a dry and wet bulb temperature acquisitiondevice performing functions of dry and wet bulb temperature acquisition,wireless data receiving and transmitting, and dry and wet bulbtemperature display.

U.S. Pat. No. 8,021,462 B2 relates to a dehumidification plant forgranular materials having varying physicochemical characteristics, withenergy consumption less than that of the dehumidification process. Thispatent also relates to a process for regenerating at least one processtower in a granular material dehumidification plant.

EP 2186613 B1 relates to a high efficiency system for dehumidifyingand/or drying plastic material. The system enables electronic processcontrol of hopper parameters monitored through sensors and devices.

U.S. Pat. No. 6,289,606 B2 relates to an apparatus and a method forcontrolling moisture content of a particulate material in a hopper. Theapparatus comprises a dew-point sensor to output a signal based on thesensed moisture content of the material and a control circuitry to causethe selector to operate based on output signal.

The existing drying process does not allow a system to provide a validdew-point value within which the system must be capable of estimatingthe total moisture content of the material. Hence, there is a need for asystem that provides an accurate real-time valid dew-point value withinwhich the moisture content of the material can be determined during thematerial drying process.

SUMMARY

The present invention is related to a system and method for accuratelymeasuring the real-time dew-point value of a material based on which thetotal moisture content of the material is determined. The methodcomprises of acquiring data from temperature sensors and dew-pointsensors that are positioned at dryer outlets while performing thematerial drying process. The method receives the sensed data at a serverfrom the sensors by using any of the existing data transmittingtechnologies such as Programmable Logic Controller (PLC), relay, orwireless sensor networks. Further, the method estimates the initialmoisture content of the material before the drying process begins andestimates the total moisture content of the material at any instanceduring the drying process. The method measures a valid dew-point of thematerial by determining an inflection point for the material anddetermines the total moisture content of the material based on theinflection point of the material.

Other objects and advantages of the embodiments herein will becomereadily apparent from the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 illustrates a system used in a material drying process accordingto an embodiment of the present invention.

FIG. 2 illustrates the system components required for accuratelymeasuring the real-time valid dew-point value of a material based onwhich the total moisture content of the material is determined accordingto an embodiment of the present invention.

FIG. 3a and FIG. 3b illustrates a graphical representation of thedew-point measure for different materials according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

In the following detailed description, a reference is made to theaccompanying drawings that form a part hereof, and in which the specificembodiments that may be practiced is shown by way of illustration. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the embodiments and it is to be understood thatthe logical, mechanical and other changes may be made without departingfrom the scope of the embodiments. The following detailed description istherefore not to be taken in a limiting sense.

In accordance with the present invention, the method uses an algorithmfor accurately measuring the real-time valid dew-point value of amaterial and the total moisture content of the material is estimatedwithin the determined valid dew-point value during the material dryingprocess. The material used during the drying process can be a resin, aplastic, or the like.

FIG. 1 illustrates a system used in a material drying process. Thesystem 100 comprises of a dryer unit 101 used as a material dryer byblowing dry air into the unit 101 and a hopper 102 used to maintain themoisture level of the material. The temperature and dew-point sensors103 are fixed at the dryer outlet for acquiring the data input from thehopper 102 to determine the temperature and the real-time validdew-point value of the material. The sensor data acquired from thehopper 102 is sent to the server 104 for estimating initial moisturecontent of the material before starting the drying process. In apreferred embodiment, the system 100 can determine the moisture contentof the material when the material is being dried through the dryingprocess using an algorithm. A valid dew-point value 105 for the materialinside the dryer unit 101 is determined by using an algorithm and aninflection point is determined for the material. In a preferredembodiment, the total moisture content of the material is determinedbased on the inflection point estimated for the material by using thealgorithm The real-time valid dew-point value of the material isautomatically determined and is transmitted to the hopper 102 fordetermining the total moisture content of the material within the validdew-point value by using the algorithm.

FIG. 2 illustrates the system components 200 required for accuratelymeasuring the real-time valid dew-point value of a material based onwhich the total moisture content of the material is determined. Thesystem 200 comprises of the following components: a Sensor Module 201configured to sense temperature and dew-point data of the material inthe hopper 102, a Data Acquisition Module 202 configured to acquire thesensed data in the Server 104 for processing the acquired data and anAnalyzer Module 203 configured to estimate the valid dew-point of thematerial and total moisture content of the material by implementing analgorithm. The algorithm determines the valid dew-point value of thematerial as follows: Total mass of water vapor U(t) that has been forcedout of the dryer at a given time t, can be obtained from the equation

U(t)=k∫ ₀ ^(t) DP(t′)*D _(Air)(t′)*F(t′)dt′  [1]

Where DP(t′) is the dew-point at a given time t′ in the outlet,D_(Air)(f) is the density of air (since outlet air temperature ischanging) and F(t′) is the flow rate, which remains same all the time. Alinear correction factor of k is assumed because dew-point measurementis never accurate and it is to offset the inaccurate dew-point.

Then water extracted from plastic between any two given points t and t2,is given by

ΔU(t−t2)=k∫ _(t2) ^(t) DP(t′)*D_(Air)(t′)*F(t′)dt′  [2]

To measure the moisture content of plastic as V(t), following massconservation equation is applied denoting total mass of plastic as Mp,

Mp*{V(t)−V(t2)}=ΔU(t−t2)=k∫ _(t2) ^(t) DP(t′)*D _(Air)(t′)*F(t′)dt′  [3]

Assuming t2=0^(th) time or any other time from several sets ofmeasurement of drying, k is determined from linear regression which issupposed to remain constant as it reflects dew-points calibrationadjustment.

Knowing k, total amount of water in plastic material can be estimated aswell as remaining water in plastic or alike material can be determined.

In an embodiment, the following algorithm is used to determine theinitial moisture content of the plastic:

$\begin{matrix}{{V(0)} = {\left( \frac{k}{Mp} \right){\int_{0}^{\infty}{{{DP}\left( t^{\prime} \right)}*{D_{Air}\left( t^{\prime} \right)}*{F\left( t^{\prime} \right)}{t^{\prime}}}}}} & \lbrack 4\rbrack\end{matrix}$

Since within 15-30 minutes of outlet air attaining highest and saturatedtemperature, plastic moisture content is expected to reduce to 50-100parts per million (ppm), practically, we can use an equation, (assumingTd is the time to arrive at high-saturated temperature at outlet of thedryer):

$\begin{matrix}{{V(0)} \cong {\left( \frac{k}{Mp} \right){\int_{0}^{1.5*{Td}}{{{DP}\left( t^{\prime} \right)}*{D_{Air}\left( t^{\prime} \right)}*{F\left( t^{\prime} \right)}{t^{\prime}}}}}} & \lbrack 5\rbrack\end{matrix}$

Vapor content of plastic at top at any given time during materialcycling:

$\begin{matrix}{{V(t)} = {{V(0)} - {\left( \frac{k}{Mp} \right){\int_{0}^{t}{{{DP}\left( t^{\prime} \right)}*{D_{Air}\left( t^{\prime} \right)}*{F\left( t^{\prime} \right)}{t^{\prime}}}}}}} & \lbrack 6\rbrack\end{matrix}$

A Controlling Module 204 is configured to transmit data across modulesin the system 200 by using any of the existing data transmittingtechnology such as Programmable Logic Controller (PLC), relay, andwireless sensor networks and so on.

FIG. 3a and FIG. 3b illustrates a graphical representation of thedew-point measure for different materials. As depicted in FIG. 3a , asthe temperature of the drying air is increased for the nylon material,the moisture content or the dew-point value of the nylon material isdecreasing during the drying process. Further, as the temperature of thedrying air is increased during the drying process the valid dew-pointfor the material decreases. As depicted in FIG. 3b , as the drying airis blown into the dryer unit 101, over a period the valid dew-pointvalue of the material eventually decreases. In a preferred embodiment,the method automatically transmits the estimated valid dew-point valueto the hopper 102 within which the total moisture content of thematerial can be determined by the algorithm For example: one materialdepicts a dew-point of 2000 ppm and the other material depicts adew-point of 770 ppm that has decreased over a period of time during thematerial drying process. The algorithm must determine the total moisturecontent of the material within the valid dew-point value estimated forthe material.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the embodiments herein that others can, byapplying current knowledge, readily modify and/or adapt for variousapplications such specific embodiments without departing from thegeneric concept, and, therefore, such adaptations and modificationsshould and are intended to be comprehended within the meaning and rangeof equivalents of the disclosed embodiments. It is to be understood thatthe phraseology or terminology employed herein is for the purpose ofdescription and not of limitation. Therefore, while the embodimentsherein have been described in terms of preferred embodiments, thoseskilled in the art will recognize that the embodiments herein can bepracticed with modification within the spirit and scope of the appendedclaims. Although the embodiments herein are described with variousspecific embodiments, it will be obvious for a person skilled in the artto practice the invention with modifications. However, all suchmodifications are deemed to be within the scope of the claims.

1. A method for accurately measuring the real-time valid dew-point valueof a material within which the total moisture content of said materialis determined, wherein said method comprises: acquiring data fromtemperature and dew-point sensors positioned at dryer outlets; receivingthe sensed data at a server after transmitting the acquired data byusing programmable logic controller (PLC), relay, or wireless sensornetworks; estimating initial moisture content of said material beforethe drying process begins; estimating moisture content of said materialat any instant during the drying process; measuring a valid dew-point bydetermining an inflection point for said material; and determining thetotal moisture content of said material after determining saidinflection point.
 2. The method as claimed in claim 1, wherein saidmethod estimates the initial moisture content of said material bypassing the acquired data through a set of equations implemented in saidserver.
 3. The method as claimed in claim 1, wherein said methodestimates the moisture content of said material at any instant duringthe drying process by passing the acquired data through another set ofequations implemented in said server.
 4. A system for accuratelymeasuring the real-time valid dew-point value of a material for whichthe total moisture content of said material is determined, wherein saidsystem comprises of an analyzer module and said system is configured to:acquire data at a server from temperature and sensors positioned atdryer outlets; receive the sensed data at said server after transmittingthe acquired data by using programmable logic controller (PLC), relay,or wireless sensor networks; estimate initial moisture content of saidmaterial on said server by using an algorithm before the drying processbegins; estimate moisture content of said material at any instant duringthe drying process by using said algorithm; measure a valid dew-point bydetermining inflection point for said material by using said algorithm;and determine the total moisture content of said material afterdetermining said inflection point by using said algorithm.
 5. The systemas claimed in claim 1, wherein said system estimates the initialmoisture content of said material by passing the acquired data through aset of equations implemented in said server.
 6. The system as claimed inclaim 1, wherein said system estimates the moisture content of saidmaterial at any instant during the drying process by passing theacquired data through another set of equations implemented in saidserver.